The present invention relates generally to fiber optic rotary joints, and more particularly, to a fiber optic rotary joint that can receive multiple different signals during rotation of the rotor. Even more particularly, the present application relates to parallel data transmission through segmented waveguides of large diameter.
The patent application entitled xe2x80x9cSectional Waveguides for Large Diameter Fiber Optic Rotary Jointxe2x80x9d describes an example of a fiber optic rotary joint having eight source fibers (of equal length, 45xc2x0 spacing), two sectional waveguides (22.5xc2x0 in length, 55xc2x0 spacing) and two pickup fibers (of equal length, positioned at ends of a respective waveguide). The same modulated light source is applied to each of the eight source fibers and is received by the two pickup fibers, and recovered through summation of the light output from the two pickup fibers. The described configuration minimizes the difference in propagation delay between the signals, which reduces pulse distortion and jitter when the optical signals are summed. The reduction in pulse distortion and jitter allows for higher data rates to be transmitted through the fiber optic rotary joint than is possible with a continuous waveguide. Referring now to FIG. 1, sufficient optical power necessary must be maintained to achieve a specified bit error rate (BER) with the arrangement illustrated in FIG. 1. For example, the same BER performance as disclosed in the patent application entitled xe2x80x9cSectional Waveguides for Large Diameter Fiber Optic Rotary Jointxe2x80x9d can be achieved with a single short section of waveguide with one pickup fiber (RX 0). However, a single short section of waveguide with one pickup fiber (RX 0) will require 16 sources (TX A, TX B . . . TX P) to maintain the optical power level for a specified BER. As depicted in FIG. 1, only 22.5xc2x0 of the 360xc2x0 ring is actively being used for signal transmission.
Thus, a need exists in the art for a segmented waveguide that utilizes a large portion of the ring for signal transmission. Another need exists for a segmented waveguide which can handle multiple individual data streams.
It is, therefore, an object of the present invention to utilize a large portion of the ring diameter for signal transmission.
It is another object of the present invention to increase the data rate that can be transmitted through the fiber optic rotary joint.
Yet a further object of the present invention is to transmit up to eight separate channels of information across a fiber optic rotary joint.
Still a further object of the present invention is to transmit eight individual data streams or an eight byte parallel data stream through the fiber optic rotary joint.
The present invention is directed to a fiber optic rotary joint comprised of multiple segmented waveguides. Each of the multiple segmented waveguides is located on the stator. The segmented waveguides are circumferentially spaced from each other. Spaces between the segmented waveguides are non-reflective. Each of the segmented waveguides has an optical pickup. There are a plurality of optical transmitters located on the rotor. In the preferred embodiment there are sixteen transmitters with eight transmitters transmitting at one time and eight transmitters turned off at that time. Although the present invention is typically used in conjunction with a cat scan machine, the present invention is also usable with any other device that requires a rotary joint.
Rather than transmitting a single serial data stream through the large fiber optic rotary joint 100 which is limited to the maximum data rate of the sectional waveguide 110-180, the present invention transmits eight individual serial data streams or an eight bit parallel word data stream through the large fiber optic rotary joint 100. By using an encoder or resolver, the position of each source fiber relative to the eight waveguides can be determined to a very high degree of accuracy. The information generated by the encoder or resolver will feed a high speed-switching network. The eight individual channels of data or one eight-bit parallel channel are fed into the switcher. The switcher is used to route the input data to the appropriate source fiber such that continuity is maintained between a specific input channel and a specific waveguide/pickup fiber receiver.
These and other objects of the present invention are achieved by providing a fiber optic rotary joint including a first plurality of optical waveguide segments attachable to a stator. Each of the optical waveguide segments has an optical pickup. A second plurality of optical transmitters is located on a rotor and rotatable therewith. A position determining device determines a circumferential location of at least one of the plurality of optical transmitters during rotation thereof. A switch routes optical signals to be transmitted by the second plurality of optical transmitters to be received by a predetermined one of the optical pickups.
The foregoing and other objects of the present invention are achieved by providing a method of transmitting multiple optical signals through a fiber optic rotary joint having a first plurality of segmented waveguide segments on a stator. Each of the segmented waveguide segments has an associated optical receiver and a second plurality of optical transmitters on a rotor. A position is determined for each of the second plurality of optical transmitters during rotation of the rotor. Based upon the position of the plurality of optical transmitters, each of the multiple optical signals is routed to a predetermined one of the segmented waveguides.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.